Due to industrial design requirements for usability, aesthetics, etc., it is generally desirable to reduce the thickness of an electronic device, for example, a notebook computer or cellular phone. However, for mi electronic device equipped with a camera, given image quality requirements, thickness reduction may be limited by the track length of the camera, as discussed with the reference to the examples of FIGS. 1A-B.
FIG. 1A illustrates a schematic representation of an example prior art electronic device 100 equipped with a color camera 110. Color camera 110 may be installed in a display module 102, which includes a display unit 104.
FIG. 1B illustrates a schematic representation of a partial cross-sectional view through line A-A of electronic device 100 indicated in the example of FIG. 1A. As illustrated in the example of FIG. 1B, color camera 110 may include a lens 112 configured to receive reflected light from an object.
Color camera 110 may also include a sensor area 116. Sensor area 116 may include an array of photo sensors (typically charge coupled device or CCD) configured to collect/receive luma data (i.e., data pertaining to light intensity) and chroma data (i.e., data pertaining to color) from lens 112.
Color camera 110 may also include an optical filter 114 disposed between lens 112 and sensor area 116. Optical filter 114 may be configured to differentiate colors according to wavelengths.
Sensor area 116 may be supported by a substrate 122. Substrate 122 may be electrically coupled with a flex circuit 118 by electrical interconnect 124. Flex circuit 118 may be connected to one or more computing and logic units in electronic device 100.
The total track length L of color camera 110 may represent the distance between the apex of lens 112 and the bottom of flex circuit 118.
For electronic device 100, the thickness t of display unit 104 is less than the total track length L of color camera 110. Accordingly, the thickness T of display module 102 may be primarily determined by the total track length L of color camera 100.
In order to reduce thickness T of display module 102, total track length L of color camera 100 may need to be reduced. Given a specified field of view F, reducing total track length L may require reducing the size of sensor area 116.
The size of sensor area 116 may be reduced by reducing the number of photo sensors in sensor area 116. However, if the number of photo sensors is reduced, the luma data and chroma data received for constructing an image of the object may be insufficient. As a result, the quality of the constructed image may be compromised.
The size of sensor area 116 may also be reduced by reducing the pitch, or the distance between every two adjacent photo sensors. However, if the pitch is reduced, the light received by the photo sensors may be insufficient. Accordingly, the signal-to-noise ratio for the received data may be low. As a result, the image quality may not be acceptable. Given that optical filter 114 generally may have a low transivity for light, it may be essential to have sufficiently large photo detectors in order to receive a sufficient amount of light. Larger detectors reduce the number of pixels available in a given sensor size.
The size of a color image sensor may be reduced if the number of pixels of the color image sensor is reduced. However, the luma received by the color image sensor may not be sufficient. As a result, the quality of the reconstructed image will be compromised.
As can be appreciated from the foregoing discussion, to provide acceptable image quality, total track length L of color camera 110 may need to be maintained, or even enlarged. Accordingly, thickness T of display module 102 that houses color camera 110 cannot be easily reduced.